In the maintenance of swimming pools, cooling towers, and the like, it is a routine practice to provide some means for purifying the water to eliminate the build-up of bacteria and algae in the water. Most of these systems employ recirculated water; so that the water which is purified is recirculated back through the system on a continuous basis.
A relatively common solution for the purification of water, particularly in swimming pools, is to add chlorine in the form of liquid chlorine compounds, or in the form of solid compounds, such as pellets or granules, to control bacteria growth. These chlorine compounds are added, either continuously or intermittently, by supplying them directly into the pool water. Particularly when such compounds are added intermittently, the chlorine level in the pool fluctuates considerably. As a consequence, the control of the bacteria and the algae in the water is imprecise.
In an effort to eliminate or substantially minimize the amount of chlorine which is to be added to a pool or cooling tower system, electrochemical ionization systems have been devised. One such system is disclosed in the patent to Henson U.S. Pat. No. 4,525,272. The device disclosed in this patent is an electrolytic water purification apparatus, which kills algae and bacteria while eliminating the use of chlorine or other toxic chemicals, or at least minimizing the use of such chemicals for purifying the water.
In the device disclosed in the Henson patent, a constant direct current is passed between a copper anode and a steel cathode immersed in a recirculating stream of water with which the device is used. The device produces copper ions, which kill algae and bacteria in the water passing through the device. Oxygen produced at the cathode promotes the decomposition and oxidation of bacteria in the water. The Henson device, however, still generally requires some additional means for completely eliminating algae and bacteria, particularly when it is used in cooling towers and similar applications.
For large commercial swimming pools and cooling towers, chlorine gas frequently is injected into the recirculating water in measured amounts for producing the desired purification. In such systems, bottled chlorine gas typically is used; and this gas is bled into the pool water as required. The size of such systems, and the expense of the hardware employed, however, generally limit bottled chlorine gas systems to relatively large commercial pool systems or cooling tower systems.
Efforts have been made to generate chlorine gas from a media liquid, such as brine or hydrochloric acid (HCl) for utilization in a water purification system capable of being used in home or backyard swimming pool systems, as well as large commercial pools. This is accomplished by electrolytic cells, which employ an anode and cathode immersed in a brine or HCl solution to cause a decomposition of the solution into components including chlorine gas. The chlorine gas which is produced then typically is mixed with the recirculating water of the pool in a venturi mixer, or is bubbled through the water by some other technique.
Five patents which illustrate electrolytic chlorinators using a brine solution are the patents to Kirkham U.S. Pat. No. 3,669,857; McCallum U.S. Pat. No. 4,085,028; Persson U.S. Pat. No. 4,136,005; Richards U.S. Pat. No. 4,439,295; and Collier U.S. Pat. No. 4,555,323. These patents all disclose different devices to produce, electrolytically, chlorine gas from a brine solution The gas which is produced then is supplied to some type of mixer, which injects it into the water. The byproducts from "brine" generators of these devices include caustic sodium.
Two patents, to Russell U.S. Pat. No. 4,381,240 and Carlsson U.S. Pat. No. 4,701,265, disclose chlorine generators employing hydrochloric acid for the media liquid. Both of these patents also disclose different devices utilizing vertically oriented anodes and cathodes, which are immersed, at least partially, into the acid. Direct current is applied across the electrodes causing the acid to decompose, generating chlorine and hydrogen gases. The chlorine gas then is bubbled into the water to be dissolved therein.
In the various patents of the prior art mentioned above, the systems are operated essentially as non-pressurized systems. A safety problem can exist if, for some reason, excess chlorine gas is generated and produces a relatively high pressure. The gas also is highly caustic; and provisions must be made to prevent pressure build-up. In addition, since all of the foregoing patents employ vertically oriented electrodes, if the liquid medium, whether it is brine or hydrochloric acid, drops to some low level, current still passes between the electrodes. This means that a relatively large volume or space can be produced above the low liquid level; and this space is filled with chlorine gas. Since the electrodes extend through the chlorine gas, a spark can be produced between the elctrodes, resulting in an explosion, since chlorine gas is highly explosive in nature. As a consequence, there is an inherent danger of explosion in such systems. Consequently, liquid level sensors frequently are employed to terminate operation of the electrolytic chlorinators in the event the media liquid drops below some pre-established level. If a malfunction, however, should exist in the sensor for accomplishing this, the dangerous condition still exists. These systems do not have a "fail-safe" mode of operation.
It is desirable to provide an electrolytic chlorination device, which overcomes the disadvantages of the prior art, which is highly effective in the production of chlorine from liquid media, which operates with inherent safety features, and which produces no hazardous byproducts.